German patent document DE 43 41 409 Al discloses a headlight illumination field regulating apparatus having an electromagnetic radiation emitter, a reflected radiation sensor, an evaluation unit, and a unit for adjusting the alignment position of the headlights. The electromagnetic radiation emitter operates to radiate electromagnetic radiation on the road to the front of the automobile and the reflected radiation sensor senses reflected radiation and creates a data point representative of the irradiated spot.
The evaluation unit evaluates the data points to establish the position of the detected spot or area and thereafter compares the evaluated position with a predetermined desired position and subsequently generate a correction signal to control the regulation or adjustment of the headlights into a proper light projecting orientation which ensures a proper projection limit of the beam of the headlight.
In the event that the inclination of the vehicle in the fore and aft direction-namely, relative to its direction of travel--changes, this disclosed regulating apparatus can accommodate such inclinations and control the orientation of the headlights to maintain the proper projection limit of their beams. However, imprecision in the regulation of the headlights can arise from the circumstance that the projection limit of the headlight beam is influenced by changes in the height of the vehicle as well as by changes in its inclination. This imprecision is magnified the smaller the projection limits of the headlight beam.